1. Field of the Invention
The present invention is directed to a housing and an electrode lead adapter for a heart stimulator.
2. Description of the Prior Art
An implantable pacemaker (pacer) is a system composed of a pulse generator and the pacing lead(s) connected thereto. At the proximal end of each pacing lead is a male plug (terminal pin) which is connected to the pulse generator, and at the distal end of the lead there is (at least) one electrode adapted to be implanted in (or in the vicinity of) a patient""s heart. The pulse generator normally has a housing (xe2x80x9ccasexe2x80x9d or xe2x80x9ccanxe2x80x9d), which contains a battery and electronic circuitry, and a connector (xe2x80x9cheaderxe2x80x9d). The connector is a receptacle into which said pacing lead(s) is (are) inserted.
The internal parts of the pacer must be well protected, especially against body fluids, for a long time period. This places strict requirements on all entries into the interior of the housing, especially on the lead connection to the housing. It should also be possible to disconnect the pulse generator from the implanted lead(s), e.g. for replacement or servicing of the generator. The connective parts of the pulse generator and the lead(s) have largely been standardized to include in practice a relatively deep female socket having internal contact surfaces, while the male plug (at the proximal end of each lead) has corresponding external contact surfaces.
Conventionally the connective pulse generator housing part containing the female socket is made of a transparent material, usually a medical grade epoxy resin, which is molded onto the housing and onto contacts protruding from the housing. The lead""s male plug is normally locked in the connector receptacle by means of a set-screw or some other fastening means. However, the positioning and alignment of the contact surfaces and of the fastening means or metallic threads for the set-screw, prior to the molding of the connective part, is very complicated, and the delay in the manufacturing process incurred by the curing of the epoxy is considerable.
Thus, it would be desirable that such a molding procedure could be dispensed with.
It has been considered that a possibility of avoiding these problems might be to design a pulse generator which is provided with a female socket located inside its metal housing, however, such an integrated socket, sometimes called a xe2x80x9cblack holexe2x80x9d, is presently not used.
U.S. Pat. Nos. 4,262,982, 4,934,366 and 5,324,311 describe interior sockets or blind holes in pacemaker housings. In all cases the interior socket has a tubular member formed of a number ofjoined sections of different materials, e.g. metal and insulating ceramics. A metallic end section of the tubular member can be welded or bonded to an opening in the pacemaker housing by means of an exterior flange on the end section. However, the use of sections of different materials in the tubular member makes the assembly procedure more complicated and demanding regarding precision and durability of the components. The integrity of the interior of the housing also must be guaranteed during a very long period of implantation.
U.S. Pat. No. 5,007,864 discloses a lead-to-pacemaker adapter which allows the use of a smaller diameter terminal electrode lead assembly than that for which the pacemaker was designed. The adapter permits direct electrical connection from the terminal pin electrode (at the proximal lead end portion) to the pacemaker connector block and its terminal set screw, without any intermediate connecting elements.
The adapter is tubular and includes a cylindrical body which tapers at its rear open end to an extension. At its forward closed end the adapter has an end face from which an electrically conductive half-round tube extends outwardly. On its underside the adapter has a retaining bump provided for latching the adapter in place within a receptacle cavity in the pacemaker""s head portion. Near the outer opening of the receptacle cavity there is a small hole along the bottom side thereof. When the adapter is inserted in place within the receptacle cavity said retaining bump engages within said small hole.
When the terminal pin electrode at the proximal lead end portion has been inserted into the adapter, the pin electrode will be positioned in the channel-shaped half-round tube at the forward end of the adapter. A socket recess set screw, which is threaded into the connector block, is brought into contact and locking engagement with said pin electrode, thereby retaining the lead assembly in firm mechanical and electrical coupling to the pacemaker.
U.S. Pat. No. 4.583.543 discloses an upsizing adapter for electrically and mechanically coupling a small size terminal electrode assembly (which is mounted at the proximal end of a pacing lead) to a large size terminal electrode assembly socket in a pacemaker. The adapter is adapted to be inserted into the electrode assembly socket in the pacemaker, and the electrode assembly at the proximal end of the pacing lead is inserted into a socket in the adapter. Thus, the smaller terminal electrode assembly at the lead""s proximal end is received and held in a larger size socket in the pacemaker by means of the adapter. The adapter with the pacing lead electrode assembly inserted therein is retained in the pacemaker socket by means of an Allen set screw in a connector block within an upper body portion of the pacemaker. A pointed tip of the set screw forces a side wall portion of the adapter""s forward end tube (enclosing the lead""s terminal pin electrode) into contact with the lead""s terminal pin electrode. In this way, an electrical and mechanical connection is provided between the pin electrode and the connector block.
A primary object of the invention is to provide a tubular connector for a pulse generator housing that is suitable for so called black holes.
A further object is provide a connector which produces a mechanically locking, electrical connection of a proximal lead end portion to the lead connection unit in a pacemaker or some other type of pulse generator.
Another object of the invention is to design a tubular connector, as well as an adapter suitable for that type of connector, which facilitates the connection of an undersized proximal lead end electrode assembly to the receiving cavity of the lead connection unit of a heart stimulator.
A still further object is to provide a connector including a tubular, male plug receiving member or barrel being designed to be optimized from a manufacturing as well as a strength-of-material standpoint.
The above objects are achieved in accordance with the principles of the present invention in a metallic pulse generator housing having a tubular connector adapted to receive a proximal lead end plug, the connector being located inside the housing and having a closed end within the housing and an open end that is welded or bonded to an opening in a wall of the housing. The connector is formed by a metallic barrel which is weldable or bondable to the metallic housing, and has a structurally unitary tube member with a cavity containing electrical contacts for contacting contact surfaces on the lead end plug. At least one insulating substrate is arranged in or on a region of the barrel wall which defines the cavity. The substrate has contacts on a surface thereof facing into said cavity.